Date of Award

Spring 2023

Document Type

Open Access Thesis

Department

Civil and Environmental Engineering

First Advisor

Shamia Hoque

Abstract

Experiments were performed to study floc formation in water bodies. In particular, the study aimed to systematically identify effects of water depth, time, salinity, initial clay concentration, and clay type on floc formation and settling. Three sediment types were chosen for this research are Three sediment types were chosen for this research: silica powder, with particle sizes comparable to clay flocs, kaolin clay and bentonite clay. Silica was chosen as a control because it did not form flocs. Kaolin represented low activity clay; bentonite was chosen as the high activity clay. Experiments lasted up to 48 hours. Graduated cylinders were set up for static trials varying initial sediment concentration and salinity. Collection dishes were placed at the bottom of each cylinder to collect the settled sediments which allowed for mass balance. Concentration and floc formation data were collected at various depths and times. Floc measurements and data were performed from microscope images. Suspended concentration data was taken from turbidity measurements and filtering. Results from kaolin clay tend to be more variable than both bentonite clay and silica powder. Silica powder stratifies the quickest of the three, as it has the coarsest particles and does not form flocs. Floc data from kaolin suggests that flocs are slower to form, are larger, and there are fewer than in bentonite experiments. Whereas, with bentonite, the data suggests the flocs form quicker, are smaller, and there are more than in the kaolin experiments. Settling rate and layer stratification speed up with the introduction of salt into the system for all sediments, as they settle out of the column quicker than in freshwater experiments.

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